Advertisement

Advertisement

Mystery radio bursts blamed on black hole ‘blitzars’

By Govert Schilling

MYSTERIOUS radio bursts from the distant cosmos are revealing their true nature. They may be the death cries of a collapsing neutron star being severed from its magnetic field as it turns into a black hole.

In 2007, the first fast radio burst (FRB) was detected. Blinking stars called pulsars emit periodic radio flashes, but this event seemed much farther away than any known pulsars, suggesting immense power. Since then, only one more FRB had been seen. Now Dan Thornton of the University of Manchester, UK, and colleagues have discovered four more using a telescope in Parkes, Australia (Science, doi.org/m5h).

With new data, they determined that FRBs can emit as much energy in a few milliseconds as the sun puts out in a million years. They also say that FRBs are common, with each galaxy producing one about every 1000 years – it’s their short duration that make them hard to spot.

What could give rise to FRBs? Heino Falcke of Radboud University in Nijmegen, the Netherlands, and Luciano Rezzolla of the Max Planck Institute for Gravitational Physics in Potsdam, Germany, blame the explosion of a giant star. It could leave behind an overweight neutron star that cannot collapse to a black hole because of the centrifugal effect of its spin. After a few million years, however, its magnetic field slows the spin and the star collapses. “The magnetic field will be cut off from the star and snap like rubber bands,” says Falcke, producing a giant radio flash (arxiv.org/abs/1307.1409).

Advertisement

The magnetic field will be cut from the star and snap like rubber bands. This can produce a giant radio flash

The radio waves come from around the star so can escape the collapse, unlike wavelengths that come from the star itself. This can explain why FRBs – which Falcke and Rezzolla call “blitzars” – unusually emit purely at radio wavelengths. Thornton, however, favours magnetars – highly magnetic neutron stars – as the source of FRBs.

This article appeared in print under the headline “Radio flashes may be noise of black hole births”